1. Field of the Invention
The present invention relates to an inner shield arranged in a color braun tube for shielding an external magnetism or magnetic field such as an earth magnetism exerting a harmful influence upon a deflection of an electron beam, more particularly, to an inner shield for a color braun tube, enabling an inside of the color braun tube to be maintained in a higher vacuum state by scattering barium(Ba) contained on a getter into an inside of the inner shield easily in such a case that the getter disposed in an inside of the braun tube is heated by a high frequency.
2. Description of the Related Art
In general, as shown in FIGS.1 and 2, a surface of the inner shield 5' is provided with an opening portion 8' so that when the getter 6' is heated by the high frequency, barium (Ba) on the getter 6' can be scattered into the inner shield arranged in the color braun tube.
Upon heating the getter, barium is scattered within a range of a scattering angle as shown in FIG.1.
Accordingly, when the getter 6' is heated by the high frequency, a part of barium is not passed through the opening portion 8' and attached around the opening portion 8'.
Barium (Ba), therefore, can not absorb a suspension, oxygen, gas and etc. with any more. As a result, the internal vacuum state of the color braun tube is dropped undesirably, so that the quality of the color braun tube is deteriorated.
Moreover, barium attached around the opening portion 8' is peeled from the surface of the inner shield due to an external impact, for example, an external magnetic field. In this state, when an arc is occurred, it has a problem that the color braun tube may be blown up, and apertures of a shadow mask may be clogged up.